The present invention, in one of its aspects, relates to a viscosimeter comprising a Zahn cup, supply means arranged to supply a liquid, the viscosity of which is to be measured, to the Zahn cup, control means of the supply means operable to stop the supply of liquid to the Zahn cup once the latter has been filled to overflowing, and timing means arranged to measure the time taken for the Zahn cup to empty following operation of the said control means.
Thus the present invention relates to viscosity measurement, more especially, but not exclusively, to the measurement of the viscosity of ink used in a printing process, and the control of the viscosity in dependence upon that measurement. The invention is applicable to the measurement and control of the viscosity of any fluid where such control may be effected by the addition of a viscosity-changing fluid.
Hitherto, such measurement and control has been effected automatically by positioning an upper outlet and a bottom outlet of a Zahn cup above respective levers of a switching arrangement. The cup is filled, and the time between the successive instants when the two levers no longer have fluid impinging upon them is measured to provide a value of the viscosity of the fluid. This involves a complex construction of levers, pivoting means therefor, and means to detect the positions of the levers so as to determine whether or not liquid is impinging on them.
The present invention seeks to simplify measurement of the viscosity of a liquid using less complex means to measure the time taken for fluid to flow out from the Zahn cup.